Acrochaetium infestans howe et hoyt

Acrochaetium infestans Howe et Hoyt, endozoic in Obelia, is reported for the first time from the British Isles, and the diagnostic evidence briefly summarized.     

Role of epidermal growth factor and ErbB2 receptors in 3T3-L1 adipogenesis

Objective: Epidermal growth factor (EGF) stimulates proliferation in 3T3‐L1 preadipocytes, but EGF action in differentiation is less clear. EGF promotes differentiation at concentrations <1 nM but inhibits differentiation at higher concentrations, suggesting a dual role in adipogenesis. We hypothesized that differences in EGF receptor activation and downstream signaling mediate distinct biological effects of EGF at low vs. high abundance. Research Methods and Procedures: We compared the effects of low (0.1 nM) vs. high (10 nM) EGF on the activation of EGF receptors, proximal signaling molecules Src and Shc, and the downstream mitogen‐activated protein kinase (MAPK) pathways extracellular regulated kinase (ERK) and p38 in proliferating and differentiated 3T3‐L1 cells. Results: Both low and high EGF activated ERK and p38 in preadipocytes. Src inhibitors PP1 and PP2 blocked ERK and p38 activation by low but not high EGF, and only high EGF increased Shc phosphorylation. Selective inhibition of the EGF receptor (EGFR) with AG1478 blocked ERK and p38 activation at both concentrations; however, selective inhibition of the ErbB2 receptor (EB2R) with AG825 or small interfering RNA (siRNA) blocked low but not high EGF activation of ERK and p38. Coimmunoprecipitation of EGFR with EB2R and Src was observed with low EGF in preadipocytes but at both concentrations in adipocytes. EB2R inhibition during differentiation decreased p38 activity and peroxisome proliferator‐activated receptor γ (PPARγ) abundance. Discussion: Our results show that EGFR homodimers mediate action of EGF at high abundance, but at low abundance, EGF promotes differentiation through EGFR/EB2R heterodimer activation of Src and p38. These results may partially explain the observations that high EGF concentrations inhibit, whereas low concentrations support, preadipocyte differentiation.     

Broad-spectrum anti-human immunodeficiency virus (HIV) potential of a peptide HIV type 1 entry inhibitor

The AIDS epidemic continues to spread at an alarming rate worldwide, especially in developing countries. One approach to solving this problem is the generation of anti-human immunodeficiency virus (HIV) compounds with inhibition spectra broad enough to include globally prevailing forms of the virus. We have examined the HIV type 1 (HIV-1) envelope specificity of a recently identified entry inhibitor candidate, HNG-105, using surface plasmon resonance spectroscopy and pseudovirus inhibition assays. The combined results suggest that the HNG-105 molecule may be effective across the HIV-1 subtypes, and they highlight its potential as a lead for developing therapeutic and microbicidal agents to help combat the spread of AIDS.     

Inhibition of insulin-like growth factor-I mitogenic action by zinc chelation is associated with a decreased mitogen-activated protein kinase activation in RAT-1 fibroblasts.

The mechanisms responsible for the resistance to the anabolic actions of IGF-I induced by zinc deficiency are not understood. We showed that zinc chelation by DTPA (diethylenetriaminepenta-acetic acid) inhibits [3H]thymidine incorporation stimulated by IGF-I in Rat-1 fibroblasts. This inhibition was specific of zinc chelation since it was prevented by the addition of zinc to DTPA. The stimulation of MAPK, which is crucial for the [3H]thymidine incorporation induced by IGF-I in Rat-1 cells, was partially blunted by DTPA. Therefore, the inhibition of the mitogenic action of IGF-I in Rat-1 fibroblasts by DTPA is potentially caused by decreased MAPK activation by IGF-I.     

Effects of diatom mucilage on the growth and Morphology of marine algae

Germination and growth patterns were studied of germlings and sporelings of eight species of marine algae when grown on diatom mucilage. Whilst growths of green and brown algae were enhanced, growth of the red algae was inhibited. Morphologically abnormal sporelings of Ulva lactuca L. and Gigartina stellata (Stackh.) Batt. were obtained in the presence of the mucilage.     

Direct evidence that the protein kinase catalytic subunit mediates the effects of cAMP on tyrosine aminotransferase synthesis

The effect of purified beef heart cAMP-dependent protein kinase catalytic subunit on tyrosine aminotransferase activity in intact cultured rat H35 hepatoma cells was directly tested by micro-injection using human red blood cell ghosts as vehicles. Although the micro-injection procedure itself produced temporary fluctuations in protein synthesis and in tyrosine aminotransferase activity in H35 cells, after a recovery period of 8-12 h, these parameters returned to normal in parallel with restoration of full inducibility of the aminotransferase by both 8-Br-cAMP and dexamethasone. Eight to sixteen hours after fusion of H35 cells with unloaded ghosts, ghosts loaded with bovine serum albumin or mock-loaded with the partially purified protein kinase catalytic subunit, no significant change in the activity of the aminotransferase was detected. In contrast, fusion with ghosts loaded with the catalytic subunit at concentrations between 0.1-2 mg/ml caused reproducible 2-3-fold increases in enzyme activity. Homogeneous preparations of the catalytic subunit exhibited even greater potency as an inducer. The effect was both time- and concentration-dependent and was abolished by inactivation of the catalytic subunit with N-ethylmaleimide prior to loading. The partially purified inhibitor of protein kinase from beef heart, while not affecting basal tyrosine aminotransferase activity, selectively inhibited the ability of 8-Br-cAMP but not that of dexamethasone to stimulate the activity of this enzyme. In addition, micro-injection of the pure regulatory subunit of the kinase blocked the response of the aminotransferase to low concentrations of 8-Br-cAMP. These results provide strong support for the proposition that the catalytic subunit of protein kinase mediates the effects of cAMP on the synthesis of tyrosine aminotransferase.     

Growth,salinity tolerance and extracellular carbohydrate yield of Prasinocladus marinus (Cienk.) Waern (class prasinophyceae)

Growth of Prasinocladus marinus (Cienk.) Waern was maximal in media of 35‰ salinity, showing a five-fold increase over a 7-day period. At lower salinities (10–27.5‰) growth varied between 55–90% and at 45‰ was 85% of that in ‘normal’ sea water. Yield of extracellular carbohydrate was higher than in ‘normal’ sea water in lowered salinities and at 45‰ over a 42-day period. Larger quantities of extracellular carbohydrate were obtained at all stages of growth in media of 15‰, compared with those of 35‰ and 45‰. Whilst growth forms were markedly different at low salinities, DNA measurements indicated that similar quantities of cell material were present. Mannitol and glucose were the principal carbohydrates identified in intracellular material, and glucose in the extracellular products. Chloroplast pigment synthesis appears unaffected by growth at 15‰, 35‰, and 45‰.     

The endoplasmic reticulum is the site of cholesterol-induced cytotoxicity in macrophages

Excess cellular cholesterol induces apoptosis in macrophages, an event likely to promote progression of atherosclerosis. The cellular mechanism of cholesterol-induced apoptosis is unknown but had previously been thought to involve the plasma membrane. Here we report that the unfolded protein response (UPR) in the endoplasmic reticulum is activated in cholesterol-loaded macrophages, resulting in expression of the cell death effector CHOP. Cholesterol loading depletes endoplasmic reticulum calcium stores, an event known to induce the UPR. Furthermore, endoplasmic reticulum calcium depletion, the UPR, caspase-3 activation and apoptosis are markedly inhibited by selective inhibition of cholesterol trafficking to the endoplasmic reticulum, and Chop-/- macrophages are protected from cholesterol-induced apoptosis. We propose that cholesterol trafficking to endoplasmic reticulum membranes, resulting in activation of the CHOP arm of the UPR, is the key signalling step in cholesterol-induced apoptosis in macrophages.     

Enrichment of endoplasmic reticulum with cholesterol inhibits sarcoplasmic-endoplasmic reticulum calcium ATPase-2b activity in parallel with increased order of membrane lipids: implications for depletion of endoplasmic reticulum calcium stores and apoptosis in cholesterol-loaded macrophages

Macrophages in advanced atherosclerotic lesions accumulate large amounts of unesterified, or "free," cholesterol (FC). FC accumulation induces macrophage apoptosis, which likely contributes to plaque destabilization. Apoptosis is triggered by the enrichment of the endoplasmic reticulum (ER) with FC, resulting in depletion of ER calcium stores, and induction of the unfolded protein response. To explain the mechanism of ER calcium depletion, we hypothesized that FC enrichment of the normally cholesterol-poor ER membrane inhibits the macrophage ER calcium pump, sarcoplasmic-endoplasmic reticulum calcium ATPase-2b (SERCA2b). FC enrichment of ER membranes to a level similar to that occurring in vivo inhibited both the ATPase activity and calcium sequestration function of SERCA2b. Enrichment of ER with ent-cholesterol or 14:0-18:0 phosphatidylcholine, which possess the membrane-ordering properties of cholesterol, also inhibited SERCA2b. Moreover, at various levels of FC enrichment of ER membranes, there was a very close correlation between increasing membrane lipid order, as monitored by 16-doxyl-phosphatidycholine electron spin resonance, and SERCA2b inhibition. In view of these data, we speculate that SERCA2b, a conformationally active protein with 11 membrane-spanning regions, loses function due to decreased conformational freedom in FC-ordered membranes. This biophysical model may underlie the critical connection between excess cholesterol, unfolded protein response induction, macrophage death, and plaque destabilization in advanced atherosclerosis.